Flynn stepped down from his post after a series of revelations surrounding conversations he had with the Russian ambassador prior to Trump's inauguration. It was reported Wednesday that Harward, now an executive at Lockheed Martin, had been offered the job, and at a press conference Thursday, Trump boasted that he had found an "outstanding" replacement for Flynn.

But Harward has rejected Trump's offer, CBS confirmed on Thursday, although the president has reportedly asked him to return to the White House in an attempt to change his mind.

Think about it: Harward is a former Navy Seal. And he felt the WH was too big a mess to take on. https://t.co/6kwxZF8RMD

Harward was one of three names believed to be in contention for the job, alongside former CIA Director David Petraeus and retired Lt. Gen. Keith Kellogg, who is currently the acting National Security Advisor. One report alleged that Trump is also considering Stephen Hadley, who served as National Security Advisor under George W. Bush, for the role.

Kellogg advised Trump on policy during the campaign, and was one of the original contender's for the job ultimately given to Flynn. Hadley is a former Navy officer and Defense Department analyst, and served on the National Security Administration during Gerald Ford's presidency. Petraeus has held several top military posts and is generally respected by Republicans and Democrats alike; however, appointing him as the top advisor on national security matters would likely draw controversy, due to the the fact that he pled guilty to mishandling classified information in 2015.